Hooke's Law - Springs

Enduring Understanding:

At the macroscopic level, forces can be categorized as either long-range (action-at-a-distance) forces or contact forces.

3.C.4 Contact forces result from the interaction of one object touching another object, and they arise from interatomic electric forces. These forces include tension, friction, normal, spring (Physics 1), and buoyant (Physics 2).

3.C.4.1 Make claims about various contact forces between objects based on the microscopic cause of these forces. [SP 6.1]
3.C.4.2 Explain contact forces (tension, friction, normal, buoyant, spring) as arising from interatomic electric forces and that they therefore have certain directions.

∆x = 0 m ∴ F= 0 N

∆x = 0.10 m ∴ F= 3.4 N

In this case we can see that a force of 3.4 N was needed to extend a spring 0.10 m.

Work is being done on the system, W=FΔd, therefore energy is being put INTO the spring.

What is about ropes/springs that determine their strength?

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Strength - is a measure of the force needed to break a material.

Flexibility - is how easily the material will bend when a turning force is applied.

Fatigue - is the loss in strength due to repeated applications of stress, for example bending, leading to fracture (breaking).

Elasticity - is the property which allows a material to regain its shape when a force is removed.

Complete 2 of the following experiments/data collection opportunities.

The main properties to be considered when selecting a rope for a particular use are:

breaking load for a given diameter size;
fatigue performance on bending;
resistance to abrasion (wear);
resistance to corrosion;
resistance to deformation (changing shape);
elasticity.

Hooke's Law and Properties of Springs

Data Collection:

Choose 4 springs to compare.
Describe the different characteristics of the springs you have chosen.
Design a method to compare the strength of the springs. Complete the following table to organize your thoughts.

Analysis:

Explain the significance of the slope of your graph and any intercepts?

If your graph does not pass through the origin, where did the error occur in your data collection?

Link to Google Sheets: Hooke's Law / Spring Data

2. Stretching Copper Wire

Using ~20cm of copper wire set up as shown. Gently add 200g masses each time and try to be very accurate when measuring the extension of the wire. Record the results in a table and plot a graph as before.

Analysis:

Explain the significance of the slope of your graph and any intercepts?

If your graph does not pass through the origin, where did the error occur in your data collection?

3. Springs in Parallel - PIVOTInteractives

Following the Link in GOOGLE CLASSROOM, complete the investigation of Parallel Springs in PIVOTInteractives.

Wire Breaking Point

A group of students is investigating how the thickness of a metal wire affects the maximum force Fmax with which the wire can be pulled without breaking. Two students are discussing models to represent how Fmax depends on wire thickness.

Student A claims that Fmax is directly proportional to the radius of the wire.

Student B claims that Fmax is directly proportional to the cross-sectional area of the wire—the area of the base of the wire, shaded gray in the figure above.

Part A: For a wire of radius r0, it is determined that Fmax is F0, as indicated by the dot on the grid below. On the grid, draw and label graphs corresponding to the two students’ models of the dependence of Fmax on wire radius. Clearly label each graph “A” or “B,” corresponding to the appropriate model. Copy of Graph Paper can be found HERE.

Part B: The table below shows results of measurements taken by another group of students for wires of different thicknesses.

In a Google Sheet, plot the appropriate data points from the table. Clearly scale and label all axes, including units. Draw either a straight line or a curve that best represents the data.

Minimum breaking strength and safe load for Bright wire, uncoated, fiber core (FC) wire rope, improved plow steel (IPS):

Part C: Which student’s model is more closely represented by the evidence shown in the graph you drew in part (c) ?

____ Student A’s model: Fmax⁡ is directly proportional to the radius of the wire.

____ Student B’s model: Fmax⁡ is directly proportional to the cross-sectional area of the wire.

Explain your reasoning.

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